Method for inhibiting corrosion of ferrous metals with 1-hydroxybenzotriazoles

ABSTRACT

A corrosion inhibiting composition which comprises an aqueous medium having dissolved therein an effective amount of at least one of water-soluble 1-hydroxybenzotriazole compounds and watersoluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of   WHEREIN X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methoxy group, carboxy group and cyano group.

United States Patent [191 Tanaka et al.

22 Filed: Feb. 2, 1973 21 Appl. No.: 329,081

[30] Foreign Application Priority Data Feb. 5, 1972 Japan 47-013046 1521 US. Cl 428/457; 21/2.7 R; l48/6.14;

[51] Int. Cl. C23f 11/14 [58] Field of Search 252/392, 403; 260/308 B, 260/308 R; 117/127; 148/6.14, 31.5; 21/25 [56] References Cited UNITED STATES PATENTS 3.425954 2/1969 Ruzevick et a1. 252/392 FOREIGN PATENTS OR APPLICATIONS 2.003.827 7/1970 Germany 1577581 6/1969 France ..260/308B OTHER PUBLICATIONS Chemical Abstracts, American Chemical Soc., Vol. 73 11970), 66583F.

[4 1 July 15, 1975 Primary Examiner-Benjamin R. Padgett Assistant Examinerlrwin Gluck Attorney, Agent, or FirmArmstrong, Nikaido & Wegner 1 5 7] ABSTRACT A corrosion inhibiting composition which comprises an aqueous medium having dissolved therein an effective amount of at least one of water-soluble 1- hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble l hydroxybenzotriazole compound having the formula of N n N/N wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methoxy group, carboxy group and cyano group.

7 Claims, No Drawings METHOD FOR INHIBITING CORROSION OF FERROUS METALS WITH l-HYDROXYBENZOTRIAZOLES This invention relates to an aqueous corrosion inhibiting composition and a method for inhibiting corrosion of ferrous metals, such as iron, steel and iron alloys.

in the prior art sodium nitrate and amine-based surfactants are known as water-soluble corrosion inhibitors and have been extensively used for protecting ferrous metals from corrosion. However, such known inhibitors are not sufficient in practical uses. Although sodium nitrate displays an excellent corrosion inhibiting effect on ferrous metals which are brought into contact with water having dissolved therein said inhibitor. for example, the effect reduces markedly when ferrous metals coated with the inhibitor is placed in the air. Further, the nitrite has a considerable toxicity, causing water pollution when exhausted to water system without post-treatment. Amine-based surfactants are insufficient in corrosion inhibiting effect in air as well as in water and will sometimes disturb cooling and washing operations due to marked foamability thereof. Ferrous metals treated with the amine-based surfactants. moreover, can not be subjected to parkerizing treatment or coated with paints without removing the surfactants attached thereto. When the surfactants are to be removed, a complicated procedure such as electrolysis is necessary, since it can not be washed off with an alkali solution.

An object of the invention is to provide a composition and method for inhibiting corrosion of ferrous metals which are free from the drawbacks of the conventional inhibitors.

Another object of the invention is to provide a corrosion inhibiting composition which displays an excellent corrosion inhibiting effect on ferrous metals not only in water but also in air.

Another object of the invention is to provide a corrosion inhibiting composition which is low in toxicity and can be exhausted free from water pollution.

Another object of the invention is to provide a corrosion inhibiting composition which has no foamability and therefore can be added to cooling or washing water without adversely affecting cooling or washing operationv Another object of the invention is to provide a corrosion inhibiting composition which makes it possible to directly subject ferrous metals treated therewith to parkerizing treatment or coating with paints.

Another object of the invention is to provide a corrosion inhibiting composition which can be easily removed from the surface of ferrous metals treated therewith, as desired.

These and other objects of the present invention will be apparent from the following description.

The corrosion inhibiting composition of the present invention comprises an aqueous medium having dissolved therein an effective amount of at least one of water-soluble l-hydroxybenzotriazole compounds and watersoluble salts thereof, said water-soluble lhydroxybenzotriazole compound having the formula of wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms, nitro group, halogen atom, sulfo group, methoxy group, carboxy group and cyano group; preferable X and Y being hydrogen atom, a lower alkyl group having 1 to 3 carbon atoms or nitro group.

According to the researches of the present inventors it has been found that when ferrous metals are treated with the l-hydroxybenzotriazole and its derivatives specified above, they are effectively protected from corrosion not only in water but also in air. Such effect can not be expected from benzotriazole per se, as known in the art, which displays a corrosion inhibiting effect only on copper and its alloys but little or no effect on ferrous metals. The reason why the lhydroxybenzotriazoie and its derivatives can display such marked effect on ferrous metals has not been made clear yet, but is supposedly attributable to the fact that the surface of ferrous metals is covered with a monomolecular film of chelate compound formed between iron atom and l-hydroxybenzotriazole or its de rivatives to be shut off from air and/or water, whereby the ferrous metals are effectively protected from corrosion.

Moreover, ferrous metals treated with the present composition can advantageously be subjected to parkerizing treatment or coated with paint without removal of l-hydroxybenzotriazole or its derivatives therefrom. W hen ferrous metals treated with the present composition are to be chemically or electrically plated, lhydroxybenzotriazole or its derivatives attached thereto can easily be removed from the metal surface by simple procedures, for example, by washing with an alkali solution.

The l-hydroxybenzotriazole and derivatives thereof to be used in the invention are l-hydroxybenzotriazole compounds having the formula (1) before and watersoluble salts thereof. Representative examples of the l-hydroxybenzotriazole compounds are lhydroxybenzotriazole, l-hydroxy-4-methylbenzotriazole, l-hydroxy- 6-nitro-benzotriazole, l-

hydroxy-S-chloro-benzotriazole, l-hydroxy-o-sulfobenzotriazole, l-hydroxy-5-methoxy-benzotriazole, lhydroxy-S-cyano-6methyl-benzotriazole, l-hydroxy-6- carboxy-benzotriazole, l-hydroxy-S-isopropylbenzotriazole, etc. Also employable in the invention are water-soluble salts of the above 1- hydroxybenzotriazole compounds. Such salts include,

for example, ammonium salts, alkali metal salts, hydrazine salts and amine salts.

Of the above l-hydroxybenzotriazole and derivatives thereof preferable are l-hydroxybenzotriazole, lhydroxy4-methyl-benzotriazole, l-hydroxy-onitrobenzotriazole and water-soluble salts thereof.

The l-hydyroxybenzotriazole compounds to be used in the invention are known in the art and can be prepared, for example by the reaction of hydrazine with o-chloronitrobenzene having or not having one or two substituents.

Ferrous metals to which the present composition is applied include iron and its alloys such as carbon steel, mild steel, stainless steel, cast iron, etc.

The l-hydroxybenzotriazole and derivatives thereof to be used as corrosion inhibitor in the invention are water-soluble, so that they can be applied to the ferrous metals in the manner conventional to water-soluble corrosion inhibitors. For example, ferrous metals may be brought into contact with the present corrosion inhibitor by coating them with an aqueous solution of the inhibitor, followed by drying, or by adding the inhibitor to water to be brought into contact with the ferrous metals. In the latter case, the present inhibitor is added to water such as cooling water in the rolling of ferrous metals, cooling water in a cooling system, washing water for pickled or degreased ferrous metals, etc. Since the present inhibitor is thermally stable, it displays an excellent corrosion inhibiting effect in various temperature conditions, for example, in primary cooling water of near C in winter as well as in cooling water of about 60 to 80C in rolling operation.

The effective concentration of the present inhibitor varies over a wide range depending on the application method, kind of ferrous metals to be treated, etc., but it displays a sufficient effect in such a small concentration as 0.05 wt.%. Since the present inhibitor has little or no toxicity, it can be used in any large amount. But it is preferable to use the inhibitor in a concentration of 0.05 to 10 weight percent from economical view point. Particularly, when the present inhibitor is used in the form of an aqueous solution for coating ferrous metals, preferable concentration of the inhibitor in solution is in the range of 0.5 to 5 weight percent. When the present inhibitor is added to water with which ferrous metals are brought into constant, preferable con- EXAMPLE 1 Various amounts of l-hydroxybenzotriazoles shown in Table 1 below were respectively dissolved in water at C, and the resulting solutions were adjusted with monoethanolamine to a pH of 7.5 to prepare compositions having varying concentrations according to this invention.

Corrosion inhibition test and toxicity test were conducted using the compositions thus obtained.

l. Humidity Cabinet Test Cold-rolled steel sheets (JlS-G-3l4l, Class I), each measuring 60 mm X mm X l.2 mm, were polished by polishing paper (JlS-R-6252, No. E240), washed with kerosene at 50C and further with methanol at 50C. The resulting steel sheets were then immersed in the abovementioned compositions for 30 seconds respectively, dried and thereafter placed in humidity cabinets according to JlS-Z-0228 to inspect corrosion produced in predetermined periods of time. The results are given in Table l which also shows the results of treatments likewise conducted using a 1 wt.% aqueous solution of sodium nitrite as sample No. 6 and water as sample No. 7 respectively. centration thereof in the water system is in the range of 0.05 to 1.0 weight percent.

Various additives can be added to the present composition in order to improve the properties thereof. For example, water-soluble high molecular weight substances are added thereto to further improve the corrosion inhibiting effect on ferrous metals. Examples thereof are polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, starch, polyacrylic acid, styrene-maleic acid copolymer, etc. Further, surfactants are added in order to improve wettability of ferrous metals to be treated with the present composition. Examples of such surfactants are nonionic surfactants such as polyoxyethylene alkylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene nonylphenyl ether, etc.; cationic surfactants such as quaternary ammonium salts, etc.; anionic surfactants such as ammonium salt of alkylbenzenesulfonate, sodium salt of polyoxyethylene nonylphenyl ether sulfate, etc.

For a better understanding of the present invention examples are given below.

TABLE 1- Continued Sample Corrosion inhibitor used Corrosion" No. 24 72 I20 168 240 hrs. hrs. hrs. hrs. hrs.

N ll N X Y Amount used l Sodium C E nitrate) 7 lWater) E Note: "The resulting corrosion was evaluated according to 1151-2912 based on the following criteria:

Symbol Degree of corrosion A B l C 1 l D 26 E 5| 100 ll. Indoor Weathering Test Various test pieces shown in Table 2 were polished 30 The results of the tests (I) and (II) indicate that the compositions of this invention exhibit outstanding corrosion inhibiting effects on steel and iron.

[I]. LD Test The test was conducted using male Wistar rats after 24 hours fasting weighing 150 g, each 10 rats as a group. An aqueous solution containing 25% by weight of l-hydroxybenzotriazole ammonium salt I OH No. 20 and water as sample No. 21 respectively.

Table 2 Sample Test piece Corrosion inhibitor used Corrosion No. X 24 72 I20 168 240 360 hrs. hrs. hrs. hrs. hrs. hrs. N ll N X Y Amount used .8 CR8 H H 0.5 A A A A B C 1.0 A A A A A A to 3.0 A A A A A A l HRS" l.0 A A A A A A l2 4-CH 1.0 A A A A B C l3 5--Cl A A A A B D l 4 H 6-SO H A A A C E l5 6-NO A A A A A A 16 Cl 5-OCH H A A B B C C l7 Cl 5CN 6CH,-, 1.0 A A A A B B l8 -H 6-CO0H I A A A B B B CH l9 CH- CH4 --H A A B B c E CH 20 CRS' A B D E .11 lWa- B E ter) Note:

"Criteria of corrosion an: the same as in test (I).

"CR5 is cold-rolled steel of JlS-G-3l4l. Class 1, measuring mm X mm X 1.2 mm.

"HRS is hot-rolled stcel ofJlS-G-3l3l, measuring 60 mm X 80 mm X 8 mm. "Cl is cast iron of .llS-G-SSOI. Class 3. measuring 60 mm X 80 mm X 5 mm.

was forcible administered orally to the rats and the rats were raised for l week in a constant temperature and constant humidity chamber at a temperature of 22C and humidity of 65%. The LD as determined by Table 4 shows that the present composition is very effective in inhibiting corrosion in the surface of ferrous alloy in contact with circulating water.

What we claim is:

l. A method for inhibiting corrosion of a ferrous Litchfield Wilcoxon method was 16.330 mg/kg which is about 1/180 the LD of 85 mg/kg for sodium nitrile metal comprlss Fomammg a ferrous metal as determined in rats. This indicates that the present a composmo comammg an effecuve "P of at Composition is Very low in toxicity least one of watersoluble l-hydroxybenzotnaaoie compounds and water-soluble salts thereof, said water- IV. Acute Toxicity Test '0 soluble l-hydroxybenzotriazole compound having the l-hydroxybenzotriazole was dissolved in water at formula varying concentrations, and ten killifishes measuring X 2.5 to 3 cm in length were placed into each solution \5 A and raised for 24 hours. The median tolerance limit N (TLm) as determined according to JIS-K-OlOZ was about 800 ppm. The TLm for sodium nitrite as determined by the same procedure was 10 to 13 ppm. This H shows that the present compositions were very low in toxicity to fishes and almost free of water pollution. wherein X and Y are each refsgectwely one member seected from the group consisting of hydrogen atom, a EXAMPLE 2 lower alkyl group having 1 to 3 carbon atoms, nitro l-hydroxybenzotriazole was dissolved in water at gggs gfig gg ggis gig g method), group car temperature, at Varying concentratlons and the 2. The method for inhibiting corrosion of a ferrous solutions were adjusted to pH of 3 t aOH to pr metal according to claim 1, wherein said X and Y are pare compositions of this invention. respectively one member selected from the group con- Containers of cold-rolled steel sheet (.llS-G-3 l4l sisting of hydrogen atom, a lower alkyl group 1 to 3 car- Class 1) polished and washed on the inner surface bOn atoms and nitro group. thereof in the same manner as in Example 1 (l) were The method for inhibiting q i of a q filled with the compositions thus prepared and sealed. metal accorfimg to claim wherem benzotflazole Corrosion produced in the inner surface of the concompound at least one P tainer was measured upon lapse of predetermined Periiq 'fi' f g g g gi L' ods of time according to JIS-Z-29l2, with the results y m e'mmamle' ydroxy--sulfo-benzotr1azole, l-hydroxy-5-methoxyg ven in Table 3. which also shows the results obtained benzotriazolel hydmxy 5 cyano 6 methyl without using a corrosion inhibitor. Criteria of corrobenzotriazole 1 hydmxy 6 carboxy benzotriazole and SiOll are the same as in test Of Example 1. 1-hyd o y 5-isopropylbenzotriazole Table 3 Sample Concen- Corrosion No. tration 24 48 72 as 120 240 360 480 (wt.%) hrs. hrs. hrs. hrs. hrs. hrs. hrs. hrs.

22 0.03 A A A B B B B B 23 0.1 A A A A A A A A 24 0.3 A A A A A A A A 25 E (Water) Table 3 above indicates that the present composi- 4. The method for inhibiting corrosion of a ferrous tions are very effective in inhibiting corrosion in the metal according to claim 3, wherein said benzotriazole surface of ferrous alloy in contact with still water. 50 p un is at ast n f y r xy nzotriaz l ,l-

hydroxy-4-methylbenzotriazole and l-hydroxy-6-nitro- EXAMPLE 3 benzotriazole.

A steel tube (JlS-G-3452), 300 cm in length and 4.16 5. The method for inhibiting corrosion of a ferrous cm in inner diameter, was washed with 5 wt.% acetic metal according to claim 1, wherein said effective acid and then with water. The same composition as amount is M1635 Q05 in concentration- Sample 23 m Example 2 was clrculatec} commu' 6. The method of inhibiting corrosion of a ferrous F thrQugh the Steel tuber and the resulqng com)" metal according to claim 5, wherein said effective was Inspected "P lapse of predetermined p amount is in the range of 0.05 to 10 wt.% in concentraods of time. The results are given in Table 4. tion.

Table 4 7. A ferrous metal treated for resistance to corrosion,

said resistance to corrosion resulting from the applica- Sample Concen- Corrosion tion to said ferrous metal of a corrosion inhibiting com- No. trstrgn h24 r1120 r2140 E60 600 position containing at least one of water-soluble 1- (wt. 0) rs. rs. rs. rs. rs. hrs. 55 hydroxybenzotriazole compounds and water-soluble 26 O! A A A A A A salts thereof, said water-soluble l- Notc: Criteria of corrosion is the same as in test (I) of Example I.

hydroxybenzotriazole compound having the formula 0 wherein X and Y are respectively one member of the group consisting of hydrogen atom, a lower alkyl group having 1 to 3 carbons, nitro group, halogen atom, sulfo group, methoxy group, carboxy-group and cyano 5 group. 

1. A METHOD FOR INHIBITING CORROSION OF A FERROUS METAL WHICH COMPRISES CONTACTING A FERROUS METAL WITH A COMPOITION CONTAINING AN EFFECTIVE AMOUNT OF AT LEAST ONE OF WATERSOLUBLE 1-HYDROXYBENZOTRIAZOLE COMPOUNDS AND WATER-SOLUBLE SALTS THEREOF, SAID WATER-SOLUBLE 1- HYDROXYBENZOTRIAZOLE COMPOUND HAVING THE FORMULA:
 2. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said X and Y are respectively one member selected from the group consisting of hydrogen atom, a lower alkyl group 1 to 3 carbon atoms and nitro group.
 3. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole, 1-hydroxy-4-methylbenzotriazole, 1-hydroxy-6-nitro-benzotriazole, 1-hydroxy-5-chloro-benzotriazole, 1-hydroxy-6-sulfo-benzotriazole, 1-hydroxy-5-methoxy-benzotriazole,1-hydroxy-5-cyano-6-methyl-benzotriazole, 1-hydroxy-6-carboxy-benzotriazole and 1-hydroxy-5-isopropylbenzotriazole.
 4. The method for inhibiting corrosion of a ferrous metal according to claim 3, wherein said benzotriazole compound is at least one of 1-hydroxybenzotriazole,1-hydroxy-4-methylbenzotriazole and 1-hydroxy-6-nitro-benzotriazole.
 5. The method for inhibiting corrosion of a ferrous metal according to claim 1, wherein said effective amount is at least 0.05 wt.% in concentration.
 6. The method of inhibiting corrosion of a ferrous metal according to claim 5, wherein said effective amount is in the range of 0.05 to 10 wt.% in concentration.
 7. A ferrous metal treated for resistance to corrosion, said resistance to corrosion resulting from the application to said ferrous metal of a corrosion inhibiting composition containing at least one of water-soluble 1-hydroxybenzotriazole compounds and water-soluble salts thereof, said water-soluble 1-hydroxybenzotriazole compound having the formula of: 